Polyacrylamide-based friction reducers (FRs) are widely used in hydraulic fracturing to reduce friction created within fluid as it flows through tubulars or other restrictions. These polymers generally add viscosity to the fluid to reduce the turbulence induced as fluid flows. Type and amount of total dissolved solids (TDS) in source water have significant impact on performance of FRs. This study investigates these effects and evaluates various types of FRs applied to the Marcellus Shale region.
It was found that increase in salinity often causes significant performance degradation (Mantell et al., 2011). This is especially critical for application of FRs in Marcellus shale that is known for challenging brine contents. This effect is more pronounced for some divalent cations than for monovalent ones. Addition of surfactant systems can improve FR performance by extending the salt tolerance. Overall, it can be concluded that FR optimization for given water content and proppant can be done by adjusting FR type and/or concentration. For special applications, when higher proppant loading is desired, applying Viscosifying Friction Reducers (VFRs) and High Viscosity Friction Reducers (HVFRs) are proven to be preferable. It was demonstrated that slickwater viscosity tend to increase exponentially with VFR concentration increase. At the same time VFRs should be breakable to ensure high regained proppant conductivity and minimization of formation damage. Such result would further justify the transition from traditional gelled fluids to FR-based viscous slickwater.
This comprehensive review explores the application of various types of FRs for Marcellus shale region. It defines the critical TDS levels, and types of cations that require changes in FR type or dosage. This data can benefit operators in (1) optimizing performance of the FR-based completion fluid; (2) avoiding formation damage associated with usage of unjustified additives; and (3) comparing/qualifying FRs based on their optimal range of application and economical dosage.